linux-kernel - Re: [RFC][PATCH 0/7] printk: use alt_printk to handle printk() recursive calls

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Date:   Thu, 29 Sep 2016 15:25:02 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:     Jan Kara <jack@...e.cz>, Andrew Morton <akpm@...ux-foundation.org>,
        Tejun Heo <tj@...nel.org>, Calvin Owens <calvinowens@...com>,
        linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: Re: [RFC][PATCH 0/7] printk: use alt_printk to handle printk()
 recursive calls

On Tue 2016-09-27 23:22:30, Sergey Senozhatsky wrote:
> 	Hello,
> 
> 	RFC
> 
> 	This patch set extends a lock-less NMI per-cpu buffers idea to
> handle recursive printk() calls. The basic mechanism is pretty much the
> same -- at the beginning of a deadlock-prone section we switch to lock-less
> printk callback, and return back to a default printk implementation at the
> end; the messages are getting flushed to a logbuf buffer from a safer
> context.

I was skeptical but I really like this way now.

The switching of the buffers is a bit hairy in this version but I
think that we could make it much better.

Other than that it looks like a big win. It kills a lot of
printk-related pain points. And it will not be that complicated
after all.

Best Regards,
Petr